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Computer Chips Made Rewritable with Light

Photonics.comJun 2012
NEW YORK, June 27, 2012 — A new technique for making rewritable computer chips uses laser light to control the spin of an atom’s nucleus to encode information, bringing ultrafast quantum computing a step closer to reality.

Current electronic devices, which are approaching the upper limits in processing speed, rely on etching a pattern into a semiconductor to create a chip or integrated circuit. These interconnection patterns serve as highways to shuttle information around circuits, but there is a drawback.

“Once the chip is printed, it can only be used one way,” said Dr. Jeffrey Reimer, a University of California, Berkeley, professor of chemical and biomolecular engineering.

Now, scientists from UCB and The City College of New York have looked to the emerging sciences of spintronics and quantum computing to remedy these problems. They used laser light to pattern the alignment of spin within atoms so that the pattern can be rewritten on the fly. The technique could lead to rewritable spintronic circuits.

The probe head used to send radio-frequency pulses onto the coil used for pulsed spin manipulation of a gallium arsenide (semiconductor) sample. (Images: Yunpu Li)
While conventional computing and digital electronics rely on translating electrical charges into the binary code of zeros and ones, spintronics computers use the quantum property of electron spin, which enables the electron to store any number between zero and one. This allows multiple computations to be completed simultaneously and processing power to be significantly increased.

Attempts to use electrons for quantum computing have been plagued, however, by the spin’s tendency to switch back and forth rapidly. This makes them very unstable vehicles for holding information.

To suppress the random switching back and forth of electrons, the scientists used laser light to produce long-lasting nuclear spin “magnets’ that pull, push or stabilize the spins of the electrons. This was achieved by illuminating a sample of gallium arsenide with a pattern of light, similar to how lithography etches a physical pattern onto traditional integrated circuits. The illuminated pattern aligned the spins of all the atomic nuclei, along with the electrons, all at once, creating a spintronic circuit.

Close-up of the mount used to hold a gallium arsenide (semiconductor) sample, showing the radio-frequency coil used for pulsed spin manipulation.
"What you could have is a chip you can erase and rewrite on the fly with just the use of a light beam," said Carlos Meriles, a CCNY professor of physics. Changing the pattern of light altered the layout of the circuit instantly.

"If you can actually rewrite with a beam of light and alter this pattern, you can make the circuit morph to adapt to different requirements," he said. "Imagine what you can make a system like that do for you!"

The technology of generating and harnessing light and other forms of radiant energy whose quantum unit is the photon. The science includes light emission, transmission, deflection, amplification and detection by optical components and instruments, lasers and other light sources, fiber optics, electro-optical instrumentation, related hardware and electronics, and sophisticated systems. The range of applications of photonics extends from energy generation to detection to communications and...